Harder. Not compressible(unless using an extremely strong force). Non-metal have more of a chance of breaking than metals.
Answer:
400 N
Explanation:
By the law of friction,
is the maximum frictional force, 
is the coefficient of friction and 
is the reaction on the refrigerator. On a horizontal surface, the reaction is equal to the weight of the refrigerator.
While not moving, the fricition on the refrigerator is static friction. So, 
This is the maximum frictional force and is more than the applied horizontal force of 400 N. Frictional force cannot be more than the applied force, else it would actually pull the refrigerator backwards (a strange thing, if it were to happen). It is equal to the extent of the applied force because the applied force is not enough to overcome the maximum.
Hence the frictional force is 400 N.
PS: Note that we do not use the coefficient of kinetic friction because applied force could not overcome the static friction.
<h2>
Answer: process of converting matter into energy</h2><h2>
</h2>
Nuclear fission consists of dividing a heavy nucleus into two or more lighter or smaller nuclei, by means of the bombardment with neutrons to make it unstable. In this process that takes place in the atomic nucleus, neutrons, gamma rays and <u>large amounts of energy are emitted. </u>
Then, with this division a great release of energy occurs and the emission of two or three neutrons, other particles and gamma rays.
This means fission is a process in which energy is released by the separation of the components of the nucleous of the atom.
In other words:
<h2>Matter is converted to energy .</h2>
The movements of the tectonic plates
Answer:
Conservation of momentum.
Momentum is zero after collision, no direction or speed.
Explanation:
